Testing the bulk viscosity within the f(R,T) gravity in light of DESI-DR2 observations
Abstract
We investigate the cosmological implications of the bulk viscosity within the framework of f(R,T) gravity by considering the linear model f(R,T)=R+2λT, where λ characterizes the matter--geometry coupling. Assuming a homogeneous and isotropic Friedmann--Lemaître--Robertson--Walker Universe, we derive analytical expressions for the Hubble parameter in two different scenarios: model A, corresponding to a pressureless viscous fluid (ω=0), and model B, where the equation of state (EoS) parameter is treated as a free parameter. The cosmological parameters are constrained through a Markov Chain Monte Carlo analysis. The results show that both viscous f(R,T) models provide an excellent description of the current expansion history and remain compatible with the combined observational data. Model A is slightly favored over the standard cosmological model (ΛCDM) according to AICc, reflecting the improved fit achieved with only one additional free parameter. In contrast, the BIC continues to favor the simpler ΛCDM model owing to its stronger penalty on model complexity. Although model B yields the lowest minimum χ2, the improvement is too small to justify the introduction of an additional free parameter, resulting in a statistical performance comparable to ΛCDM according to the AICc but less favorable according to the BIC.
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BibTeX
@misc{saddiki2026testing,
title = {{Testing the bulk viscosity within the f(R,T) gravity in light of DESI-DR2 observations}},
author = {Omayma Saddiki and Safae Dahmani and Taoufik Ouali and Abdelkarim Oukouiss},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00022},
eprint = {2609.00022},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00022},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Testing the bulk viscosity within the f(R,T) gravity in light of DESI-DR2 observations
AU - Omayma Saddiki
AU - Safae Dahmani
AU - Taoufik Ouali
AU - Abdelkarim Oukouiss
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00022
UR - https://arxiv.org/abs/2609.00022
AB - We investigate the cosmological implications of the bulk viscosity within the framework of f(R,T) gravity by considering the linear model f(R,T)=R+2λT, where λ characterizes the matter--geometry coupling. Assuming a homogeneous and isotropic Friedmann--Lemaître--Robertson--Walker Universe, we derive analytical expressions for the Hubble parameter in two different scenarios: model A, corresponding to a pressureless viscous fluid (ω=0), and model B, where the equation of state (EoS) parameter is treated as a free parameter. The cosmological parameters are constrained through a Markov Chain Monte Carlo analysis. The results show that both viscous f(R,T) models provide an excellent description of the current expansion history and remain compatible with the combined observational data. Model A is slightly favored over the standard cosmological model (ΛCDM) according to AICc, reflecting the improved fit achieved with only one additional free parameter. In contrast, the BIC continues to favor the simpler ΛCDM model owing to its stronger penalty on model complexity. Although model B yields the lowest minimum χ^2, the improvement is too small to justify the introduction of an additional free parameter, resulting in a statistical performance comparable to ΛCDM according to the AICc but less favorable according to the BIC.
ER -